Conventionally, the contact probe head including a number of contact probes mounted on a common base plate has been used for testing electronic devices as a part of a testing machine. Such a contact probe typically comprises a tubular receptacle, a needle member received therein, and a spring member urging the needle member out of the front end of the receptacle as disclosed in commonly assigned U.S. Pat. No. 5,004,977. The spring member typically consists of a compression coil spring, and is engaged with the receptacle at its one end and with a front end portion of the needle member at its other end. In particular, by using a needle member consisting of a continuous wire member extending from the front end to the rear end connected to the control unit of the testing machine, it is possible to achieve an extremely small electric resistance between the object to be tested and the control unit and an extremely low noise level.
Recently, the density of the wiring pattern of the printed circuit board and other electronic equipment is increased due to a general demand for compact design, and the diameter of each contact probe is accordingly desired to be reduced as much as possible. However, the reduced diameter of each contact probe means less resistance against repeated bending stress. The attention of the inventor was drawn to the fact that the bending stress tends to be concentrated in the part of the needle member situated close to the rear end of the receptacle.